The present invention relates to a rotary indexing machine having a plurality of machining stations and a plurality of work-holding devices arranged on a rotary table.
The term rotary indexing machine (also called rotary transfer machine or rotary table machine) refers to a machine tool in which a plurality of work-holding devices (called satellites below) are arranged like satellites on a rotary table (also called a plate) rotatable about a vertical indexing axis. Each satellite is provided with at least one clamping device for clamping a workpiece. A plurality of fixed machining stations for machining the workpieces carried on the satellites are provided along the periphery of the rotary table. For the multiple machining of the workpieces, the rotary table is gradually rotated or indexed further from one working position to the next, in the course of which the workpieces arranged on the rotary table are gradually moved further (or indexed) from one machining station to the next, where the workpieces are in each case machined with one or more fixed machining units. This permits multiple machining of the workpieces by means of a multiplicity of machining units in a single set-up.
DE-C2-39 41 480 discloses a rotary indexing machine having an essentially cage-like, one-piece rigid machine frame, in the wall parts of which the machining units are mounted at the various machining stations. So that the workpieces to be machined which are arranged on the rotary table can be positioned as precisely as possible relative to the tools attached to the machining units, the machine frame must be as rigid as possible. The requirements for the rigidity of the machine frame are especially high when a plurality of machining units are arranged at a single machining station, since the frame, during the simultaneous machining with the various machining units, then has to absorb the sum of the reaction and acceleration forces which occur as far as possible in a distortion-free and rigid manner, so that the machining tolerances can be maintained. In order to be able to fulfill the requirement for high rigidity, the machine frame parts of known rotary indexing machines are on the one hand designed to be extremely solid and correspondingly voluminous and on the other hand are arranged as close to the workpiece to be machined as possible, i.e. to the rotary table.
On account of the arrangement of solid, bulky frame parts, such as supports, struts, etc., in the vicinity of the rotary table, the conventional machine frames of rotary indexing machines occupy a considerable portion of the space which would actually be required for the machining of the workpieces. This problem again occurs to a considerable degree in rotary indexing machines having a plurality of machining units at a single machining station, since, inter alia, electrical and hydraulic lines to each of the machining units additionally occupy further space, which is then no longer available for the actual machining of the workpieces. The conflicting requirements, on the one hand to provide a machine frame of high rigidity in order to be able to maintain close tolerances during the machining of the workpieces, and on the other hand to create sufficient free space in the center of the rotary indexing machine in the region of the rotary table for the machining of complicated workpieces as well, are not fulfilled in a satisfactory manner in conventional rotary indexing machines.
The object of the present invention is to provide a rotary indexing machine which has a rigid machine frame and provides a large free space in the region of the rotary table for the machining of workpieces.
The solution of the object is the subject matter of the independent patent claims.
The rotary indexing machine according to the invention has a fixed machine frame, which is designed for holding a multiplicity of machining units and comprises at least one support, and a rotary table rotatable relative to the machine frame about a vertical indexing axis. To create free space for the machining of a workpiece to be arranged on the rotary table, the support is designed for the lateral attachment of at least one of the machining units.
Within the scope of the present description and the claims, the lateral attachment of the machining unit to the support is always to be understood in such a way that the machining unit is attached laterally to the support with regard to a radial direction running toward the indexing axis. The attachment of the machining unit to a side of the support enables the machining unit to be moved laterally past the support away from the indexing axis in the radial direction if required. As a result, free space can be created for the machining of the workpiece where this free space is also required, namely in the center of the rotary indexing machine in the vicinity of the indexing axis. In addition, due to the lateral attachment of the machining unit to the support, the support may also be arranged closer to the indexing axis than would be possible if the machining unit is attached to the inside, pointing toward the indexing axis, of the support, since in the latter case there must of course always be sufficient space for the arrangement of the machining unit between the inside of the support and the workpiece moved past the support on the rotary plate. The arrangement of the supports of the frame closer to the machine center proves to be an additional advantage, since the dynamic rigidity of the machine frame is thereby increased.
The support and the machining unit are preferably designed in such a way that the machining unit having a work spindle can be laterally attached to the support alternatively in a first position with essentially horizontally arranged work spindle or in a second position with essentially vertically arranged work spindle.
Furthermore, the support is preferably designed in such a way that, on one side of the support, two machining units, each with a work spindle provided with a tool, can be attached to the support one above the other in such a way that the two tools can be brought into engagement with the workpiece simultaneously, the workpiece being clamped in a clamping device arranged on the rotary table. By virtue of the fact that the workpiece is machined simultaneously with two work spindles in one working position of the rotary table, the number of working positions required for the machining of the workpiece can be reduced and the efficiency of the rotary indexing machine can be increased as a result.
The two machining units on one support side may each be designed for the traverse of their work spindles in three directions in accordance with three translatory axes of motion. As a result, the workpiece can be machined simultaneously at one machining station by means of two work spindles which are each movable independently of one another with three translatory degrees of freedom.
In a preferred embodiment of the invention, the support has two sides, to each of which at least one machining unit can be attached. The support is preferably designed in such a way that two machining units, each with a work spindle displaceable independently along three axes, can each be attached to both sides of the support one above the other in such a way that the tools on the two work spindles on one support side can simultaneously be brought into engagement with a workpiece arranged in a working position of the rotary table in front of this support side.
In the embodiment of the invention with a support which has two sides designed for attaching machining units, the two sides are preferably arranged in a wedge shape on an essentially vertically extending section of the support in such a way that the tip of the wedge is directed in the radial direction toward the indexing axis.
Owing to the fact that the support is designed in a wedge shape and is arranged in such a way that the tip of the wedge is directed in the radial direction toward the indexing axis, additional free space is created for the machining of the workpiece where this space is also required, namely in the center of the rotary indexing machine in the vicinity of the indexing axis. Since the thickness of the support increases radially outward, sufficient rigidity and stability of the support is nonetheless ensured.
Due to the narrow design of the support at its radially inner margin, the accessibility of the central part of the rotary indexing machine, in particular of the rotary table, the satellites and the indexing devices, is additionally improved. This proves to be advantageous especially during the adjustment or setting-up of the rotary indexing machine for the machining of a new lot of workpieces, in particular in the case of small lot sizes. On the whole, the ergonomics of the rotary indexing machine are improved by this measure.
In a preferred embodiment of the invention, the support is designed in such a way that the tip of the wedge encloses an acute angle of less than 90 degrees. The angle enclosed by the tip of the wedge is preferably even less than 45 degrees, an angle of approximately 30 degrees being especially preferred.
In the rotary indexing machine according to the invention, the machining units are preferably arranged on the essentially vertically extending support sections of wedge-shaped cross section. In principle, however, the machining units may also be arranged at other locations of the machine frame.
At the bottom end of the vertically extending section, a support may have a bottom support section for fastening the support to a fixed pedestal of the machine and/or to a fixed base unit of the machine, the bottom support section being angled relative to the vertically extending support section in the direction of the indexing axis of the rotary indexing machine, so that the support overall has an essentially L-shaped configuration. Furthermore, the support, at the top end of the vertically extending section, may have a top support section which is designed for connecting to the other supports of the rotary indexing machine and which in turn is angled relative to the vertically extending support section in the direction of the indexing axis of the rotary indexing machine, so that the support overall has an essentially C-shaped configuration. An annular connecting device may be provided for the connection to the other supports, this annular connecting device being firmly connected to the top support section of each of the supports in order to increase the stability and the rigidity of the frame formed by the supports.
In a further preferred embodiment of the invention, the rotary indexing machine comprises a fixed base unit and a rotary table which is rotatable relative to the base unit about a vertical indexing axis and on which a satellite provided with at least one clamping device for clamping a workpiece is arranged so as to be rotatable about a vertical satellite rotation axis relative to the rotary table. Furthermore, a satellite drive device is arranged on the rotary table, this satellite drive device moving along with the latter and permitting rotation of the satellite about the satellite rotation axis during the rotation of the rotary table about the indexing axis. In this embodiment of the invention, the satellite preferably has a shaft, which leads through the rotary table, is rotatable relative to the rotary table about the satellite rotation axis and is connected to the satellite in a rotationally locked manner and on whose end face facing the base unit a Hirth serration system is arranged. An indexing device is arranged on the base unit, the indexing device having a column or annular disk, which is linearly displaceable parallel to the indexing axis and on whose end face facing the rotary table a Hirth serration system corresponding to the Hirth serration system on the satellite shaft is arranged. The arrangement is such that, to index the satellite, the Hirth serration system of the indexing device can be displaced linearly in the direction of the rotary table in order to mesh with the Hirth serration system of the satellite and thereby effect the indexing of the satellite. To release the indexing, the Hirth serration system of the indexing device can in turn be displaced linearly in the direction away from the rotary table.
In a further preferred embodiment of the invention, the rotary indexing machine has a fixed base unit and a rotary table rotatable relative to the base unit about a vertical indexing axis. Furthermore, the rotary indexing machine comprises drive means for driving the rotary table, the drive means comprising an electrical machine designed as a directly driven rotary spindle and having a stator which is firmly connected to the base unit and a rotor which is firmly connected to the rotary table. The rotary indexing machine in this embodiment of the invention also preferably comprises a measuring device for the exact measurement of the position and the speed of the rotor relative to the stator and a circuit arrangement, comprising a cascade controller with feedback of the speed and position, for controlling the directly driven rotary spindle. A method of constructing a rotary indexing machine in this embodiment of the invention may comprise a step based on the harmonic balance method for optimizing the system parameters of the directly driven rotary spindle and of the circuit arrangement for controlling the directly driven rotary spindle. As an alternative to the directly driven rotary spindle, the drive means for driving the rotary table may comprise a conventional rotary table motor.
A rotary indexing machine according to the invention preferably has a fixed pedestal and a rotary table rotatable relative to the pedestal about a vertical indexing axis, the pedestal for collecting chips, coolants and/or lubricants being designed in a funnel shape and having surfaces inclined downward toward its center at the indexing axis. In this embodiment of the invention, for the disposal of chips, the funnel-shaped pedestal of the rotary indexing machine preferably has a funnel outlet opening onto a chip conveyor belt.
As an alternative to the funnel-shaped pedestal, a rotary indexing machine according to the invention, having a fixed pedestal and a rotary table rotatable relative to the pedestal about a vertical indexing axis, may comprise a chip conveying device arranged below the rotary table for the disposal of chips, this chip conveying device being designed for conveying the chips around the pedestal and/or around a fixed base unit of the rotary indexing machine, the chips being conveyed up to an outlet opening and falling through the latter preferably onto a chip conveyor belt. A fixed collecting device for collecting chips, coolants and/or lubricants is preferably formed and arranged in a funnel shape below the rotary table in such a way that the chips are conveyed to the chip conveying device, leading around the pedestal, essentially by the force of gravity.